The present invention relates to a blood oxygenator (artificial lung) and more specifically relates to a membrane blood oxygenator having a multi-layer structure.
Blood oxygenators are used during heart surgery to temporarily perform the function of lungs. There are several types of blood oxygenators, such as the bubble-type, the rotating disc-type, and the membrane-type. The membrane-type, in which oxygen is absorbed into and carbon dioxide is desorbed from blood through membranes made of polymers such as silicone rubber, is considered to be superior to other types because there is less damage to blood components and hence less detrimental physiological effects.
A few of the representative types of membrane blood oxygenators and a similar device known before completion of the present invention will be briefly described. The Lande-Edwards disposable membrane oxygenator (U.S. Pat. Nos. 3,540,595; 3,541,595; 3,547,271) comprises a rectangular stack of grooved plastic support plates and pairs of silicone rubber membranes sandwiched between the plates. Blood flows between the membranes, and gas flows between the membranes and the plates through the grooves. It is said that a lung of this type having a membrane area as large as 5 sq. m. is required during heart surgery of an adult.
The parallel flow hemodialyzer, i.e. artificial kidney, of U.S. Pat. No. 3,565,258 uses a stack of flat cellophane tubes and mesh spacers. Dialysate liquid flows through the tubes, and blood flows outside the tubes. A device of this type cannot be used as a blood oxygenator, since the blood channels will collapse unless the gas space inside the tubes is kept at a lower pressure than the blood side.
During heart surgery with extracorporeal circulation, the blood temperature generally drops below the body temperature as blood circulates through the extracorporeal circuit thereby exposing the blood to the room temperature, which is below the body temperature. Thus it is often necessary to raise the temperature of blood before it returns to the body. On the other hand, when a heart surgery with hypothermia is performed, it is necessary to cool the blood. In either case, the blood temperature is controlled using a heat exchanger in which blood is warmed with hot water or cooled with cool water. The disposable membrane oxygenators described above are often used along with an independent heat exchanger. Since such a heat exchanger is not disposable, it must be cleaned and sterilized after each use. Although there are few disposable bubble oxygenators with built-in heat exchangers, no disposable membrane oxygenators with built-in heat exchangers are available on the market at present.
It is the primary object of the present invention to provide a new and improved membrane blood oxygenator.
It is an additional object of the present invention to provide an integral membrane blood oxygenator-blood heat exchanger in which damage to the blood such as hemolysis and thrombogenesis is reduced by minimizing changes in velocity and direction of blood flow through the device.
Another object of this invention is to provide a compact, disposable membrane blood oxygenator of simple construction which provides efficient gas exchange and temperature control.
These and other objects of the present invention have been attained by a membrane blood oxygenator comprising a gas exchange section of multi-layer construction including alternate layers of rectangular polymer membranes and rectangular mesh spacers forming alternate gas and blood channels between said membranes, said gas channels and said blood channels being perpendicular to each other and a heat exchange section of multilayer structure including alternate layers of metal sheets and rectangular mesh spacers forming alternate blood channels and water channels, said blood channels and said water channels being perpendicular to each other. The heat exchange blood channels are extensions of the gas exchange blood channels with the blood flow sectional area of both blood channels being equal.